Figure 3.. Geminiviruses are ssDNA viruses that replicate via rolling replication forming dsDNA without a dsRNA stage.

Figure 3.

Geminiviruses are ssDNA viruses that replicate via rolling replication forming dsDNA without a dsRNA stage. Transcription is bidirectional and the transcript overlaps resulting in dsRNA of a small segment of the AC1 gene, which is indispensable for replication. DCL4 preferentially dices this into small (22nt) virus-derived RNAs (exo-siRNA) which load into Ago1 and slice mRNA transcripts arising from the AC1 gene. The cleaved mRNA can be converted by plant RDR6 into secondary siRNAs in an amplification step, which also converts other viral ss transcripts into siRNAs. An alternate fate of the viral overlapping transcript is to be extended by RDR2 and diced by DCL3 in the nucleus, where it enters Agos 4 or 6 and shuts down viral replication. However, the viruses can interfere with this shutdown at different stages.

From: HOW OLD ARE RNA NETWORKS?

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